Hybrid driving system for a motor vehicle

ABSTRACT

Hybrid drive for a motor vehicle with a drive train, comprising a combustion engine and a vehicle transmission with variable gear ratio and a first and second electrical machine which can be operated both as a motor and a generator, each of which comprises a stator and a rotor with the second electrical machine being in a permanent nonpositive connection with an input of the vehicle transmission, with a shiftable clutch each being arranged between the electrical machines and the drive shaft of the combustion engine, and with the electrical machines to be connected with each other and/or an electrical energy source via an electronic control circuit. The two electrical machines are to be arranged in a common housing, and one of the stators of the electrical machines together with the electronic control circuit and/or the other stator is accommodated on a common carrier.

BACKGROUND OF THE INVENTION

The invention relates to a hybrid drive for a motor vehicle with acombustion engine and a vehicle transmission with variable gear ratioand a first and second electrical machine which can be operated both asa motor and a generator, each of which comprises a stator and a rotor,with the second electrical machine being in a permanent nonpositiveconnection with an input of the vehicle transmission, with a shiftableclutch each being arranged between the electrical machines and the driveshaft of the combustion engine, and with the electrical machines to beconnected with each other and/or an electrical energy source via anelectronic control circuit.

Electric motors as drive motors for motor vehicles, which are suppliedwith electric energy by a battery or an on-board fuel cell permitemission-free and nearly silent driving, while being of a compactconstruction. The driving performance of purely electrically drivenvehicles, however, is heavily restricted, due to the limited storagecapacities of currently employed batteries, which is why electrovehicleshave been employed only in special areas.

Apart from purely electric drive systems, partially electric drives areknown which are also referred to as “hybrid drives”. These partiallyelectrical drive systems essentially have a combustion engine as driveunit, by means of which a high performance and large cruising range ofthe motor vehicles are achieved. As a supplement, at least oneelectrical machine is arranged between the combustion engine and thetransmission, which is arranged in series with or parallel to the drivetrain (between combustion engine and transmission) and offers theadvantages such as for example brake energy recovery and emission-freedriving.

In so-called serial hybrid drives, travelling is effected purelyelectrically with limited power in one driving range, i. e. thecombustion engine and one of the two electrical machines are atstandstill. The entire required energy is supplied from a battery. In asecond driving range, travelling is effected by means of the combustionengine which drives the second electrical machine operating as agenerator which in turn supplies the energy for the driving motor in theelectric mode. Such serial hybrid drives operate without clutches in apermanent non-positive connection.

In so-called parallel hybrid drives, starting is effected purelyelectrically by means of an electric motor which is connected with atransmission input shaft. Meanwhile, the combustion engine is atstandstill, which is disengaged from the transmission input shaft by anon-positive clutch. At a higher power requirement, e. g. exceeding acertain higher travelling speed, the combustion engine is started by theclosing of a clutch, with the combustion engine then serving as a primemover. The electric motor can then be used as an additional power sourceor a generator for charging the vehicle battery.

Problem on which the Invention is Based

The installation space in motor vehicles, in particular in passengercars, is very limited. An essential aspect is the simple mountabilityand the suitability for series production of the above described hybriddrives.

The present invention is based on the object to create a hybrid drivefor a motor vehicle, which provides for safe operation, compactconstruction, and ease of assembly and testing.

Invention Solution

According to the invention, this object is solved by a hybrid drive inaccordance with the characteristics of Claim 1. For this purpose, thetwo electrical machines are to be arranged in a common housing, and oneof the stators of the electrical machines together with the electroniccontrol circuit and/or the other stator are accommodated on a commoncarrier.

This design enables a space saving modular assembly with precedingtesting of the function of the stators and their cooperation with theelectronic control circuit. In addition, the common carrier may comprisea cooling means for cooling the stator(s) or the electronic controlcircuit, respectively.

This holds true all the more as the electrical machines, in particularwhen they are configured as alternating field machines, are operated byso-called frequency converters as electronic control circuit. Thesefrequency converters include a number of half-bridge arrangements, whichcorresponds to the number of phases of the electrical machine, which aresupplied with control signals from a actuation electronics which mayalso be incorporated, if required, in the electronic control circuit.Depending on whether the electrical machine is operated as a motor or agenerator, the electric power is taken from a rechargeable energy sourceand supplied to the electrical machine either for the desired speed orthe desired torque, or electric power is taken from the electricalmachine and converted into the required amount or phase position fordownstream loads or the rechargeable energy source, respectively. In thepreviously known arrangements, the frequency converters are arrangedseparately from the electrical machines and connected with same viamulti-phase power cables.

An example of such a configuration of a power electronics for anelectrical machine is described in DE 42 30 510 A1. Herein, the conceptis followed to arrange the electronics in a boiling water cooling bath,with the current feed lines, the control signals for the controlelectronics, etc. being routed to this pressure-tight encapsulatedarrangement via a central opening in the bottom of the capsule.

Primarily, the cabling expenditure and the electromagnetic shieldingwhich becomes necessary because of the cables between the electricalmachine and the frequency converter are problematic. Moreover, aconsiderable amount of power connectors both on the side of thefrequency converter and the side of the electrical machine is needed.Cooling of the power electronics of the frequency converter alsorequires a significant expenditure. Another problem is that the repairof such an encapsulated frequency converter is virtually impossiblewithout opening the pressure-tight capsule. Sealing the capsule can onlybe effected with considerable expenditure. Consequently, even minordefects of the encapsulated frequency converter result in itsreplacement in its entirety.

The inventive solution pursues the approach to integrate the electricalmachine(s) or its/their stator(s) and the actuation electronics on acommon carrier and to cool them by means of a common cooling means. Inother words, a load bearing cooling jacket is provided which is capableto accommodate the stators and the actuation electronics both at itsinner wall and its outer wall. This allows for a considerable saving ofspace and costs. If a repair might become necessary it is also mucheasier and less expensive to replace one or more defective modulesrather than the actuation electronics in its entirety. In addition, theinvention permits to considerably reduce the shielding expenditureagainst electromagnetic radiated interference because the high frequencypower carrying cables are much shorter than inconventional—separate—arrangements. Moreover, the wiring expenditure isconsiderably reduced because the previously common phase distributionrails on the machine side can be dispensed with.

Advantageous Developments of the Invention

In a preferred embodiment of the invention, the carrier has anessentially hollow cylindrical portion, with one stator being arrangedat its inner wall and the other stator being arranged on its outer wall.Alternatively, both stators may be arranged either on its inner wall oron its outer wall. The hollow cylindrical portion of the carrier has anessentially circular or polygonal ring-shaped cross section.

In a preferred embodiment, the cooling means is crisscrossed with fluidchannels. These may surround the electrical machine either circularly orspirally or may run essentially coaxially with the axis of rotation ofthe electrical machine(s) or with the centre axis of the carrier,respectively.

The cooling means can be integrated into the carrier already as early asduring its manufacture. This is relatively easy e.g. with a carrier madefrom pressure die-cast (aluminium) material because the cooling meanswith its fluid channels may be formed at the wall of the carrier in asimple manner. In one embodiment, the cooling means has at least oneopening in its outer wall, which extends to at least one of the fluidchannels and into which cooling elements arranged at one of the modulesof the electronic control circuit protrude. These cooling elements may,for example, be designed in the shape of ribs, webs, or pins.

In order to improve the heat dissipation both from the electricalmachine and the modules of the electronic control circuit, the coolingelements protruding into the fluid channels are designed in such amanner that they cause a turbulent flow in the fluid flowing in thefluid channels. This is effected, for example, by means of impact bladesarranged transversely to the fluid stream, guide vanes oriented towardseach other or away from one another, or the like.

To achieve a good electrical insulation and simultaneously a goodthermal coupling of the power semiconductors (MOSFETs, IGBTS, Schottkydiodes, etc.) disposed in the modules of the electronic control circuitthe cooling elements protruding into the fluid channels and/or thecovers of the modules are made from non-ferrous metal, preferably frommaterial containing copper or aluminium, or from ceramic material,preferably material containing alumina, aluminium nitride, and/orsilicon carbide.

In order to connect the components of the electronic control circuit,which are located in the modules with the stator and/or rotor coils overdistances as short as possible, essentially radially oriented cables arearranged in the carrier which extend from the stator and/or rotor coilsto the respective modules of the electronic control circuit.

Moreover, cables are arranged in the or at the carrier, which areoriented essentially along the circumference, and connect the respectivemodules of the electronic control circuit with one another. This allowsthe distribution of control signals, on the one hand, and of therequired electrical power, on the other hand, to the modules (in motoroperation) or the pick-off from the individual modules (in generatoroperation).

The carrier may also accommodate a hydraulic manifold plate at its innerwall and/or its outer wall, in particular for the automatic transmissionor other hydraulically operated assemblies in the drive train.

Further advantages and developments of the invention will becomeapparent from the dependent claims and from the embodiments described inthe following in principle with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a parallel hybrid drive for amotor vehicle.

FIG. 2 is a schematic illustration of a serial hybrid drive for a motorvehicle.

FIG. 3 is a schematic partial illustration in a longitudinal section ofan inventive hybrid drive of a first embodiment.

FIG. 4 is a schematic partial illustration in a longitudinal section ofan inventive hybrid drive of a second embodiment.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

FIGS. 1 and 2 schematically show a hybrid drive for a motor vehicle witha drive train 1, which comprises a first electrical machine 4 and asecond electrical machine 6 which is directly and permanently connectedwith a transmission input shaft 5, between a combustion engine 2 and amulti-gear vehicle transmission 3 in the form of an automatictransmission. Between the electrical machines 4 and 6, each of which iscapable of being operated as a motor and a generator, and the combustionengine 2 a shiftable clutch 7 or 8, respectively, is arranged.

In the embodiment according to FIG. 1 the first shiftable clutch 7 andthe first electrical machine 4 are arranged in a parallel side train 9which branches off the drive train 1 between the combustion engine 2 andthe second shiftable clutch 8 and form a parallel hybrid drive. Thefirst electrical machine 4 is therefore disengaged or engaged,respectively, from the or with the, respectively, combustion engine 2 bythe first clutch 7 and the second electrical machine 6 by the secondclutch 8.

In the embodiment according to FIG. 2 which shows a serial hybrid drive,the first shiftable clutch 7 and the first electrical machine 4,followed by the second shiftable clutch 8 and the second electricalmachine 6 are arranged in series in the drive train 1 from thecombustion engine 2 downstream towards the vehicle transmission 3.

In both embodiments, the first electrical machine 4 is provided forstarting the combustion engine 2. In this process, the first clutch 7 isclosed or slips. In principle, however, the starter function can beeffected by the two electrical machines 4 and 6.

The second electrical machine 6 primarily serves for the electricstarting with the combustion engine 2 disengaged. Starting is howeveralso possible with the second electrical machine 6 and the connectedrunning combustion engine 2. Here, the second clutch 8 is shifted in theslipping condition.

In the two illustrated embodiments the first electrical machine 4 isdirectly connected with a hydraulic pump 10 of the automatictransmission 3. The hydraulic pump 10 is arranged between the firstshiftable clutch 7 and the first electrical machine 4. It iselectrically driven by the first electrical machine 4, or mechanicallydriven by the combustion engine 2 via the closed first clutch 7.

As can be seen from FIGS. 1 and 2 the electrical machines 4, 6 areelectrically connected with each other via a power actuation control 11and with an electric energy source 12 in the form of a rechargeablebattery.

The first electrical machine 4 may be operated with current from thebattery 12 or via the power actuation control 11 with current from thesecond electrical machine 6. In the latter case, the second electricalmachine 6 operates as a generator, and the second clutch 8 is shifted tothe opened or slipping condition.

As an alternative, the first electric machine 4 can also be operated asa generator, with the second clutch 8 being shifted to the closed orslipping condition.

A torsional vibration damper 13 for protecting the drive train 1 againstrotational irregularities is arranged between the output shaft of thecombustion engine 2 and the first clutch 7.

FIG. 3 illustrates how the two electrical machines 4, 6 are arranged ina common housing 20 which has an essentially conical tubular shape. Analuminium pressure die-cast tube with a round cross section is insertedinto this housing 20 as a carrier 22 whose inner wall 24 has a circularcross section and whose outer wall 26 has a polygonal cross section. Atits front (in FIG. 3 right-hand) end the carrier 22 has a supportingflange 28 extending radially inwards which bears against a shaft 32 viaa bearing 30. On the outer wall at the front end of the carrier 22 astator 34 with indicated stator windings 34 a of the first electricalmachine 4 is arranged secured against rotation. Separated by an air gap37 a rotor 38 also with indicated rotor windings 38 a rotates about thestator 34 of the first electrical machine 4. The output side of therotor 38 to the first clutch 7 is not detailed herein.

At the side of the first electrical machine 4 facing away from the frontend, a further (second) supporting flange 40 extends from the outer wall26 of the carrier 22 radially outwards, which is secured at the innerwall of the housing 20. At the rear end of the carrier 22 a thirdsupporting flange 42 is formed which also extends radially outward tothe inner wall of the housing 20 and is secured thereon.

The second electrical machine 6 is accommodated at the inner wall 24 ofthe carrier 22 virtually over its entire length. The stator 44 of thesecond electrical machine 6 with indicated stator windings 44 a isattached secured against rotation at the inner wall 24 of the carrier22. Separated by an air gap 46 a rotor 48 also with indicated rotorwindings 48 a rotates about the stator 44 of the second electricalmachine 6. The output side of the rotor 48 to the second clutch 8 is notshown herein.

The electronic control circuit with several modules 36 distributed alongthe circumference is arranged between the second and the thirdsupporting flange 40 and 42 at the outer wall 26 of the carrier 22. Thestator windings 34 a, 44 a of the electrical machines are connected viacables 62 with the modules 36 of the electronic control circuit.

Cooling channels 52 are formed in the carrier 22, in which water or oilis circulating which dissipates the thermal energy from the electricalmachines 2, 4, in particular from their stators 34 and from the modules,in a heat exchanger not shown in detail to the environment.

In the embodiment shown in FIG. 3 the cooling channels 52 are routedessentially concentrically or spirally and are closed towards the outerwall 26 of the carrier 22. Thermal coupling between the modules 36 ofthe electronic control circuit and the carrier 22 is effected here byelectrically insulated, but thermally conductive plane bottom plate 36 aof the modules 36.

In its configuration shown in FIG. 4 the carrier 22 has several openings54 in its polygonal outer wall 26 with plane area portions, throughwhich cooling elements 58 of the modules 36 of an electronic controlcircuit are protruding. The cooling elements 58 are designed in such amanner that they cause a turbulent flow in the water or oil flowing inthe cooling channels 32 in order to enhance the heat dissipation fromthe modules 36 of the electronic control circuit and from the electricalmachines 4, 6.

Incidentally, the embodiments of FIGS. 3 and 4 differ from each other inthat in FIG. 3 at the outer wall of the carrier 22 one electricalmachine as external rotor motor and the electronic control circuit isarranged, while at the inner wall of the carrier 22 the other electricalmachine as internal rotor motor is arranged. In FIG. 4, however, onlythe electronic control circuit is arranged on the outer wall of thecarrier, and the two electrical machines are arranged as internal rotormotors at the inner wall of the carrier. FIG. 4 also shows how ahydraulic manifold plate 70 between the two electrical machines (or alsoat one of the outer faces of the respective machine) at the inner wall26 of the carrier 22 may extend radially inwards. The hydraulic manifoldplate 70 may therefore, if required, also take the function of the firstsupporting flange 28 extending radially inwards.

The modules 36 of the electronic control circuit have a shape which isessentially adapted to the available space and comprise electronicsincluding power semiconductors 36 b. The power semiconductors 36 bgenerating heat losses are thermally coupled with the cooling elements58.

The bottom plates 36 a of the modules 36 and the cooling elements 58 aremade from material containing copper or aluminium, from alumina,aluminium nitride or silicon carbide.

Finally, it should be noted that the drawings serve to illustrate andexplain the invention only in principle; the actual dimensions andproportions of embodiments of the invention may differ therefrom.

1. A hybrid drive for a motor vehicle with a drive train (1), comprisinga combustion engine (2) and a vehicle transmission (3) with variablegear ratio and first and second electrical machines (4,6) each of whichcan be operated both as a motor and a generator, each of which comprisesa stator (34, 44) and a rotor (38, 48), with the second electricalmachine (6) being in a permanent nonpositive connection with an input(5) of the vehicle transmission, first and second shiftable clutches (7,8) each arranged between the electrical machines (4, 6) and the driveshaft of the combustion engine (2), and with the electrical machines (4,6) connected with each other and also connectable with an electricalenergy source (12) via a power actuation control (11), with the twoelectrical machines (4, 6) arranged in a common housing (20), whereinthe two stators (34, 44) of the electrical machines (4, 6) and the poweractuation control (11) are accommodated along a circumference of acommon carrier (22) which comprises a cooler (52) integrally formed inthe common carrier for cooling the stators (34, 44) and the poweractuation control (11).
 2. The hybrid drive for a motor vehicleaccording to claim 1, characterized in that the carrier (22) has anessentially hollow cylindrical portion, with the one stator beingarranged at its inner wall (24) and the other stator being arranged atits outer wall (26).
 3. The hybrid drive for a motor vehicle accordingto claim 2, characterized in that the hollow cylindrical portion of thecarrier (22) has a cross section that is one of circular and polygonalring-shaped cross section.
 4. The hybrid drive for a motor vehicleaccording to claim 1, characterized in that both stators are arrangedeither at the inner wall or at the outer wall of the common carrier(22).
 5. The hybrid drive for a motor vehicle according to claim 1,characterized in that the carrier (22) accommodates a hydraulic manifoldplate (70) at its inner wall (24) and/or its outer wall (26).
 6. Thehybrid drive for a motor vehicle according to claim 1, characterized inthat the first shiftable clutch (7) and the first electrical machine (4)and the second shiftable clutch (8) and the second electrical machine(6) are arranged in series in the drive train (1) between the combustionengine (2) and the vehicle transmission (3).
 7. The hybrid drive for amotor vehicle according to claim 1, characterized in that the firstshiftable clutch (7) and the first electrical machine (4) are arrangedin a parallel side train (9) which branches off the drive train (1)between the combustion engine (2) and the second shiftable clutch (8) insuch a manner, that the first electrical machine (4) can be disengagedfrom the combustion engine (2) by the first clutch (7) and the secondelectrical machine (6) by the second clutch (8).
 8. The hybrid drive fora motor vehicle according to claim 1, characterized in that the firstelectrical machine(4) is connected with a hydraulic pump (10) of thevehicle transmission (3).
 9. The hybrid drive for a motor vehicleaccording to claim 1, characterized in that the first electrical machine(4) is connected with at least one of several auxiliary units of themotor vehicle for driving said at least one of several auxiliary units.10. The hybrid drive for a motor vehicle according to claim 1,characterized in that the second electrical machine (6) has a higherpower consumption/output than the first electrical machine (4).
 11. Thehybrid drive for a motor vehicle according to claim 1, characterized inthat the vehicle transmission is an automatic transmission (3).
 12. Thehybrid drive for a motor vehicle according to claim 1, characterized inthat the power actuation control (11) is divided into several modules(36) each of which being electrically connected with at least one of: a)the stator and b) the rotor coils (22, 24), with the modules (36) beingarranged distributed at the circumference of the electrical machine andcoupled with the cooler (52) of the carrier (22) in a thermallyconductive manner.
 13. The hybrid drive for a motor vehicle according toclaim 12, characterized in that the modules (36) of the power actuationcontrol (11) are radially arranged at the outside of the cooler (52).14. The hybrid drive for a motor vehicle according to claim 1,characterized in that the cooling means is formed by fluid channels (32)crisscrossing the carrier (22).
 15. The hybrid drive for a motor vehicleaccording to claim 1, characterized in that the carrier (22) comprisesat least one opening (54) to at least one of the fluid channels (52),into which cooling elements (58) protrude which are arranged at one ofthe modules (36) of the electronic control circuit.
 16. The hybrid drivefor a motor vehicle according to claim 1, characterized in that thecooling elements (58) protruding into the fluid channels (52) and/or thewall of the fluid channels (52) ae designated in such a manner that theycause a turbulent flow in the fluid flowing in the fluid channels (52).